5-(Alkoxymethyl)-2,3-pyridinedicarboximide compounds are useful as intermediates in the preparation of herbicidal 5-(alkoxymethyl)-2-(2-imidazolin-2-yl)nicotinic acid, ester and salt compounds. Methods for the preparation of 5-(alkoxymethyl)-2,3-pyridinedicarboximide compounds are rather limited, and those methods that are available may require extensive purification methods to provide high purity 5-(alkoxymethyl)-2,3-pyridinedicarboximide compounds.
European patent application number 308,084-A1 generically discloses that a 5-(alkoxymethyl)-2,3-pyridinedicarboximide compound may be prepared by reacting a substituted oxime compound with a halomaleimide compound optionally in the presence of an inorganic base. However, that method is not satisfactory because it produces a mixture that contains the desired 5-(alkoxymethyl)-2,3-pyridinedicarboximide compound and a relatively high percentage of an undesirable 5-methyl-2,3-pyridinedicarboximide compound. Arduous or time consuming purification methods are then required to obtain high purity 5-(alkoxymethyl)-2,3-pyridinedicarboximide compounds. If the mixture is not highly purified, the 5-(alkoxymethyl)-2-(2-imidazolin-2-yl)nicotinic acid, ester or salt compound prepared from the mixture will be contaminated with a 5-methyl-2-(2imidazolin-2-yl)nicotinic acid, ester or salt compound which has different herbicidal properties than the desired compound.
It is, therefore, an object of the present invention to provide a process for the preparation of high purity 5-(alkoxymethyl)-2,3-pyridinedicarboximide compounds.